1. Field of the Invention
The invention relates to the field of watercraft vessel lifts, and in particular, floating lifts for watercraft.
2. Introduction
From ancient times, sailors' concerns in regard to boat maintenance have included harmful effects associated with boats stored or moored floating and or immersed in water. Boats stored or moored while floating on their own hulls and or immersed in water are subject to damage not limited to water absorption in and through the hull, electrolysis and marine growth such as barnacles, muscles and algae.
In addition to water being a harsh environment for a watercraft, many bodies of water are also subject to severe tide changes and rocky bottom and shoreline contours. In addition to water being a harsh environment for a watercraft, many bodies of water and their surrounding shoreline are subject to severe tide variations, rocky bottom and shoreline contours and severe icing conditions which render permanent docking structures ineffective with a resulting shortage of means for mooring a watercraft.
Watercraft lifts were developed to lift a boat clear from the water when the watercraft is not in use. Generally, watercraft lifts are mechanisms boat owners can operate to lower and raise their watercraft without professional boat handling assistance or experience.
Prior art attempts deal with these problems and show varying boat lift mechanisms have been lacking in many areas. Several attempts include boat lifts utilizing variable buoyancy air chambers as lifting devices and support mechanisms as described in U.S. Pat. Nos. 4,018,179, 3,727,415 and 3,362,172. These mechanisms vary in design, however all share the common fatal flaw in if the air chamber does not sustain a seal, the air leaks, buoyancy is lost, the design fails and the watercraft lowers down into the water.
Another common disadvantage to the air chamber actuated lift is inherent instability during actuation. As water is purged from tank or conversely flooded into tank a high and low pressure differential is created; water and air shift sides causing an uneven weight distribution and instability which necessitates drawing stability from a non-inclusive third party structures such as docks, piers, seawalls and bulkheads.
Yet more prior art in the field of boat lift mechanisms show a number of designs like U.S. Pat. Nos. 3,967,570, and 3,727,415 whose fatal flaws include the requirement for attachment to and support from secondary structures, and objects such as fixed and floating docks, bulkheads and seawalls. Furthermore, these design lack an independently floating front pivot point, not allowing the pivot point to raise and lower, so as to not produce an asymmetrically forward cant, so as to not allow such a watercraft lift to more evenly engage a watercraft, be self sustainable, or operate in shallow water.
Other boat lift mechanisms prior art attempts, like U.S. Pat. No. 6,575,661, include boat lift mechanisms mounted to stationary objects such as the seafloor, a bulkhead and a stationary non floating pier or dock, for example. In all these cases a fatal flaw exists in a limitation of lifting height versus differing extreme tidal fluctuations and flooding. When the tidal fluctuation height surpasses this type of boat lift mechanisms maximum lifting height the boat could float off. This type of lift is also limited in its transportability and transferability and often requires substantial alteration to or addition of aforementioned third party support structures.
Yet more prior art in the field of boat lift mechanisms shows a number of designs like U.S. Pat. Nos. 6,964,239B2, 6,032,601, and 6,823,809 wherein fixed floatation devices are moved and manipulated to lift both the boat and the boat lift mechanisms. These boat lift mechanisms vary in design and complexity but share common traits and undesirable flaws and limitations such as their submerging of substantial moving parts of the boat lift including drive and winding mechanisms respectively.
For example, U.S. Pat. No. 6,964,239B2 is shown with a substantial amount of “base structure” “comprising: at least one parallelogram linkage supporting a cradle of boat bunks, requiring that at least one parallelogram linkage and at least one aqueous hydraulic cylinder are always underwater. This mandatory submerging and actuation during submersion of substantial moving parts and drives directly effect and degrade the boat lift mechanism in a manner similar to the way in which immersed watercraft are affected and degraded. Additional shortcomings relative to these designs include the number and complexity of moving parts and their limitations on boat sizes, hull shapes and configurations. For example, a deep draft boat or sailboat having a deep draft keel cannot enter exit, or be lifted by, this design.
Yet more prior art in the field of boat lift mechanisms attempt to combine multiple, connected, hollow, airtight floatation units to form a floatation surface, examples of which are U.S. Pat. Nos. 5,855,180 and 5,931,113. These designs require a watercraft to propel itself up and onto the floatation surface and to be pulled off of the floatation surface for launching, precluding usage of the design by watercraft having insufficient thrust and/or deep drafts such as sailboats.
There remains a need in the art for a boat lift mechanism that will lift and sustain a watercraft above the water, that floats and is self sustaining, that does not require support or stability from fixed structures, that is unaffected by fluctuation in water levels, that limits the submerging of substantial moving parts including drive and winding mechanisms, that accepts a variety of watercraft including deep draft vessels, and that eliminates the potential of air leakage associated with air chambers and associated valves, pumps and plumbing.